Method of stabilizing hydrates of sodium metaborate and single powder photographic developers containing same



Patented Aug. 3, 1954 METHOD OF STABILIZING HYDRATES OF SODIUM METABORATE AND SINGLE POW- DER PHOTOGRAPHIC DEVELOPERS CON- TAINING SAME Richard W. Henn, Arthur A. Rasch, and John I.

Crabtree, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 26, 1952, Serial No. 295,804

This invention relates to single-powder photographic developers and more particularly to a method of stabilizing hydrates of sodium metaborate, and to single-powder photographic develolJer compositions containing such stabilized salt.

Various single-powder photographic developers have been known heretofore. They may contain an organic silver halide developer component or mixtures of such components, including monomethyl p-aminophenol sulfate (Elon or metol), hydroquinone, p-aminophenol hydrochloride, p-aminophenol sulfate, pyrogallol, phydroxy phenyl glycine, catechol, diaminophenol hydrochloride, and others, with an alkali component, a stabilizing component,an oxidation inhibitor, a sequestering agent, and an antifogging component. The alkali component may be the stable hydrate of an alkali carbonate, a desiccated alkali carbonate, an alkalimetaborate, or an alkali sulfite. Generally the stable alkali carbonate monohydrate is preferred. The oxidation-preventing component may be an alkali sulfite, and the antifoggant may be potassium bromide, potassium iodide, or an organic compound.

Stabilizing components for such a single-powder developer are disclosed in Patent 2,384,592 of September 11, 1945, and include maleic anhydride, salicyclic acid, alkali metabisulfite, benzoic anhydride, orthobenzoic sulfimide, p-hthal- 1 imide, and phthalic anhydride. The latter has outstanding stabilizing properties in the presence of either sodium carbonate or borax and has been employed considerably more than the other stabilizers mentioned in the patent.

While the stabilizing efiect of the phthalic anhydride is very good, it has been employed most successfully in developer compositions having as the alkali component either sodium carbonate or sodium sulfite, or mixtures thereof; less success has been attained in the case of the important class of developers containing sodium metaborate as the alkali ingredient.

In the copending application by William J. Rogers, S. N. 210,284, filed February 9, 1951, entitled Stabilizing Agent for Single Powder Photographic Developers, now S. Patent No. 2,606,118 of August 5, 1952, boric anhydride is disclosed as an improved stabilizer for such sin- .gle powders as described above. In certain respects boric anhydride is superior to phthalic anhydride in stabilizing such powders.

However, we have found that the addition of these protectants to single-powder formulas in which the alkali ingredient is a hydrate of so- 3 Claims. (Cl. 95-88) dium metaborate such as sodium metaborate tetrahydrate does not protect the powders as fully as may be desired when exposed to certain conditions and some discoloration may be caused by the reaction between the developing agents and the alkali.

One method which has been proposed to overcome this disadvantageous situation is to sta-' bilize the sodium metaborate tetrahydrate with a gas such as carbon dioxide. Another method of stabilization specifically for sodium metaborate tetrahydrate in which part of the water of crystallization is removed by drying has also been suggested. In applying these two methods in treating sodium metaborate tetrahydrate, considerable equipment and handling is neces: sary including chemical analysis of the product and single powder developer mixtures prepared therefrom, require in most instances the further addition of the usual protectants. A much simplermethod is, therefore, desired.

It is an object of the invention to provide a method whereby hydrates of sodium metaborate' can be stabilized suitably for use in single-powder developer formulas by a more facile method than those known in the prior art.

Another object of the invention is to prepare 7 more stable hydrates of sodium metaborate than is possible by other methods.

Still another object is to stabilize hydrates of sodium metaborate by a method which does not substantially lessen their alkalinity.

, Other objects will appear hereinafter.

In accordance with the present invention we stabilize hydrates of sodium metaborate by sepafree alkali, either by volatilizing and coating them or by simple contact, and (3) heatin moves loose water and some water of crystallizationi,

'KTheheatdtreatment be accomplished at a low temperature for a long period of time (Example 4) or by treatment at a higher temperature for a shorter time (Examples 1, 2, and 3). In the extreme case (Example this heat treatment is accompanied by appreciable dehydra tion which further improves the stability of the mixture.

Suitable stabilizing compounds include those mentioned previously in this specification and of these, boric anhydride, metaboric acid and phthalic anhydride have been found to be most successful although the other stabilizing compounds are satisfactory.

Specifically, boron oxide hydrated to any degree intermediate to boric anhydride and metaboric acid is suitable.

Sodium metaborate tetrahydrate so treated can be advantageously incorporated in singlepowder formulas which do not show any indication that a reaction has taken place between the components of the mixture even after prolonged exposure to relatively high temperatures. At the same time the total amount of protectant used is generally less than that used in cases where treatment is by another method.

The following examples illustrate the method of the present invention and will also indicate the proportionate quantities in which the respective components can be mixed together in a dry form to make up single-powder developer mixtures.

Example 1 Boric anhydride was added to sodium metaborate tetrahydrate in a concentration of per cent and the mixture heated for 4 hours at 70 C. This mixture was packed in a formula consisting of:

Grams Elon 2.0 Hydroquinone 4.0 Sodium sulfite 22.5 Sodium metaborate tetrahydrate 10 per 1 cent boric anhydride 39.6 Potassium bromide 2.0

This single powder did not discolor or otherwise deteriorate when stored.

Example 2 Phthalic anhydride was added to sodium metaborate tetrahydrate in a concentration of 2.5 per cent and the mixture heated for 4 hours at 70 C. This mixture was packed in a formula consisting of:

Grams Elon 2.0

Hydroquinone 4.0

Sodium sulfite 22.5 Sodium metaborate tetrahydrate 2.5 per cent phthalic anhydride 37.8

Potassium bromide 2.0

This single powder discolored slightly after one month storage at 110 F. The addition of one gram of boric anhydride to the formula prevented discoloration altogether.

Example 3 4 Sodium sulfite 22.5 Sodium metaborate tetrahydrate 10 per 7 cent metaboric acid 39.6 Potassium bromide 2.0

This single powder d d not discolor or otherwise deteriorate on storage.

Example 4 Phthalic anhydride was added to sodium metaborate tetrahydrate in a concentration of 10 per 'cent and the mixture was heated at 40 C. for 30 days. The mixture was packed in a formula consisting of:

Grams Elon' 2.0

Hydroquinone 4.0

Sodium sulfite 22.5 Sodium metaborate tetrahydrate 10 per cent phthalic anhydride 36.9

Potassium bromide 2.0

This single powder did not discolor or otherwise deteriorate when stored for three weeks at F.

Example 5 Grams Elon 2.5 Hydroquinone 2.5 Sodium sulfite 50.0 Treated sodium metaborate-boric anhydride mixture 11.0 Potassium bromide 0.5

This single powder did not discolor or otherwise deteriorate when stored for 2 months at 110 F. However a formula using a similarly dehydrated metaborate, but one from which the boric anhydride was omitted was found to have inferior stability on storage.

We claim:

1. The method of stabilizing hydrates of sodium metaborate which comprises mixing powder like particles thereof with 2.5 to 10% by weight of a finely divided stabilizer selected from the group consisting of phthalic anhydride, boric anhydride, and metaboric acid and heating the mixture for approximately 4 hours at 70 C.

2. The product of the method of claim 1.

3. A single-powder photographic developer composition containing an organic silver halide developer and the product of the method of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,847,836 Kelly Mar. 1, 1932 1,976, 99 Russell Oct. 9, 1934 2,095,836 Russell Oct. 12, 1937 2,384,592 Bean Sept 11, 1945 2,606,118 Rogers Aug. 5, 1952 

1. THE METHOD OF STABILIZING HYDRATES OF SODIUM METABORATE WHICH COMPRISES MIXING POWDER LIKE PARTICLES THEREOF WITH 2.5 TO 10% BY WEIGHT OF A FINELY DIVIDED STABLIZER SELECTED FROM THE GROUP CONSISTING OF PHTHALIC ANHYDRIDE, BORIC ANHYDRIDE, AND METABORIC ACID AND HEATING THE MIXTURE FOR APPROXIMATELY 4 HOURS AT 70* C. 